In nature, wind and water can exert forces upon the earth's surface and carry away soil, rock and other materials. In addition, mankind's influence on the environment often exacerbates these natural erosion processes. For example, natural erosion can be accelerated by altering the course of a stream or removing foliage which would otherwise help anchor soil in place.
Soil erosion is a particular problem in areas such as riversides, stream banks, shorelines, beachfronts or other submersed areas. In these environments, the force created by flowing water current or crashing waves can, over time, carry away large amounts of earth and cause significant and costly damage to property. For example, erosion can destroy the integrity of the base of a stream bank, making it necessary to restabilize the area through an expensive process of filling and structural repair. Similarly, erosion, if not controlled, can cause valuable waterfront property to simply disappear.
Previous attempts to develop an effective, easy and efficient way of controlling erosion have not been successful. One such prior art attempt is the use of a solid wall to abut and protect the area in question. For example, a cement or log wall can be installed along the underwater base of a stream bank to prevent the stream from contacting, and thereby eroding, the bank. This approach, however, has numerous drawbacks. A solid wall is costly, difficult, and in some locations, impossible to install. Also, a wall is aesthetically not attractive.
A solid wall is also not environmentally attractive because it is not an effective method for controlling erosion. A solid wall does not dissipate the energy generated by the flow of water. Rather, water flowing along the wall will accelerate, thereby causing greater erosion to occur at those locations not protected by the wall, such as the stream or riverbed. Moreover, vegetation, which helps anchor soil and prevent further erosion from wind and rain, will not grow on a solid wall.
Some other prior art attempts to control erosion involve the use of interlocking units to help stabilize an area. In such systems, a trench is dug at the underwater base of the submersed area in question. One by one, the interlocking units are placed in a row within the trench to form a base for the protective cover. The remainder of the protective cover, or "revetment," is formed by stacking additional rows of units upon the base row until the units cover the area to be protected.
Prior art erosion control systems that feature interlocking units suffer from a variety of drawbacks. The units are large, heavy and cumbersome, making the transportation and installation of the units burdensome and expensive. Also, because the units are interlocking, they overlap one another so that a large number of units are required to cover the area being protected.
In addition, because the units are not positively connected to one another, but merely interlock with or rest against one another, one or more of the units can shift independently of the other units along any of the three dimensions. This undermines their effectiveness at erosion control and, in turn, destabilizes the area in question. Another drawback of these systems is that the density of the protective cover, i.e., the amount of space between each unit, is not easily adjustable--to adjust the density of the cover, one must go through the time-consuming and burdensome task of placing one or more spacing members on or between each individual unit.